- The `admissionregistration.k8s.io/v1beta1` versions of `MutatingWebhookConfiguration` and `ValidatingWebhookConfiguration` are deprecated and will no longer be served in v1.19. Use `admissionregistration.k8s.io/v1` instead. ([#79549](https://github.com/kubernetes/kubernetes/pull/79549), [@liggitt](https://github.com/liggitt))

- To address the possibility of dry-run requests overwhelming admission webhooks that rely on side effects and a reconciliation mechanism, a new field is being added to `admissionregistration.k8s.io/v1beta1.ValidatingWebhookConfiguration` and `admissionregistration.k8s.io/v1beta1.MutatingWebhookConfiguration` so that webhooks can explicitly register as having dry-run support. If a dry-run request is made on a resource that triggers a non dry-run supporting webhook,...

- The mutating and validating admission webhook plugins now read configuration from the admissionregistration.k8s.io/v1 API. ([#80883](https://github.com/kubernetes/kubernetes/pull/80883), [@liggitt](https://github.com/liggitt))

*   The admission webhook configurations API, part of the admissionregistration API, is now at v1beta1. Delete any existing webhook configurations before you upgrade, and update your configuration files to use the latest API. For this and the previous change, see also [the documentation](https://kubernetes.io/docs/adm...

* [alpha] Adding admissionregistration API group which enables dynamic registration of initializers and external admission webhooks. ([#46294](https://github.com/kubernetes/kubernetes/pull/46294), [@caesarxuchao](https://github.com/caesarxuchao))

a situation in which two webhooks make it impossible to delete each other. ValidatingWebhooks and MutatingWebhooks will not be called on admission requests for ValidatingWebhookConfiguration and MutatingWebhookConfiguration objects in the admissionregistration.k8s.io group ([#59840](https://github.com/kubernetes/kubernetes/pull/59840), [@jennybuckley](https://github.com/jennybuckley))

* Fixed potential deadlock when deleting CustomResourceDefinition for custom resources with finalizers....

//
// Instead of using this type, create a locally provided and used type that is well-focused on your reference.
// For example, ServiceReferences for admission registration: https://github.com/kubernetes/api/blob/release-1.17/admissionregistration/v1/types.go#L533 .
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
// +structType=atomic
message ObjectReference {
  // Kind of the referent.

- Added `podReplacementPolicy` and terminating field to job api. ([#119301](https://github.com/kubernetes/kubernetes/pull/119301), [@kannon92](https://github.com/kannon92))
- Added a new `namespaceParamRef` field to `admissionregistration.k8s.io/v1alpha1.ValidatingAdmissionPolicy`. ([#119215](https://github.com/kubernetes/kubernetes/pull/119215), [@alexzielenski](https://github.com/alexzielenski)) [SIG API Machinery and Testing]

- Introduced `v1alpha1` API for validating admission policies, enabling extensible admission control via CEL expressions (KEP  3488: CEL for Admission Control). To use, enable the `ValidatingAdmissionPolicy` feature gate and the `admissionregistration.k8s.io/v1alpha1` API via `--runtime-config`. ([#113314](https://github.com/kubernetes/kubernetes/pull/113314), [@cici37](https://github.com/cici37))

* The alpha Initializers feature, `admissionregistration.k8s.io/v1alpha1` API version, `Initializers` admission plugin, and use of the `metadata.initializers` API field have been removed. Discontinue use of the alpha feature and delete any existing `InitializerConfiguration` API objects before upgrading....